The decision by voters in Colorado and Washington state to legalize the recreational use of marijuana has left President-elect Enrique Pea Nieto and his team scrambling to reformulate their anti-drug strategies in light of what one senior aide said was a referendum that "changes the rules of the game."

It is too early to know what Mexico's response to the ballot measures will be, but Pea Nieto's top aide said the incoming administration will discuss the issue when he heads to Washington this month for meetings with President Barack Obama and congressional leaders. The decision, however, is expected to spark a broad debate in Mexico about the direction and costs of the U.S.-backed drug war here.

Mexico spends billions of dollars each year confronting violent trafficking organizations that threaten the security of the country but whose main market is the United States, the largest consumer of drugs in the world.

With Washington's urging and support, Mexican soldiers roam the mountains burning clandestine plantations filled with marijuana destined for the United States. Mexico's police and military last year seized almost as much marijuana as did U.S. agents working the Southwest border region.

About 60,000 Mexicans have been killed in drug violence, and tens of thousands arrested and incarcerated. The drug violence and the state response to narcotics trafficking and organized crime has consumed the administration of outgoing President Felipe Calderon.

"The legalization of marijuana forces us to think very hard about our strategy to combat criminal organizations, mainly because the largest consumer in the world has liberalized its laws," said Manlio Fabio Beltrones, leader of Pea Nieto's party in Mexico's Congress.

Pea Nieto's top adviser, Luis Videgaray, said Thursday that his boss did not believe that legalization was the answer. But Videgaray said Mexico's drug strategies must be reviewed in light of the legalization votes.

"Obviously, we can't handle a product that is illegal in Mexico, trying to stop its transfer to the United States, when in the United States, at least in part of the United States, it now has a different status," Videgaray told a radio station Wednesday.

Videgaray added that legalization "changes the rules of the game in the relationship with the United States" in regards to anti-drug efforts.

"I think more and more Mexicans will respond in a similar fashion, as we ask ourselves why are Mexican troops up in the mountains of Sinaloa and Guerrero and Durango looking for marijuana, and why are we searching for tunnels, patrolling the borders, when once this product reaches Colorado it becomes legal," said Jorge Castaneda, a former foreign minister of Mexico and an advocate for ending what he calls an "absurd war."

Pea Nieto has pledged to work closely with the U.S. government against powerful transnational crime organizations when he takes office next month. But he has stressed that his main goal is not to confront smugglers but to reduce the sensational violence and rampant crime — such as extortion, kidnapping, theft — that have soared in Mexico during Calderon's six years in office.

Jonathan Caulkins, an expert in the drug trade and a professor at Carnegie Mellon University, said marijuana legalization in the United States could allow Pea Nieto to resist U.S. pressure to maintain a hard line against smuggling groups.

Advocates for marijuana legalization in the United States and Mexico have often argued that ending the prohibition against pot would deny Mexican traffickers a key source of revenue. Analysts generally agree that about half of all the marijuana consumed in the United States comes from Mexico.

If Colorado and Washington state manage to legalize the trade — to produce home-grown products that can compete in price and quality against illegal Mexican imports — then revenue to Mexican drug cartels would probably decrease. But not by much.

U.S. experts who produced a landmark Rand Corp. study in 2010 when California voters were considering the legalization of recreational marijuana use (the measure did not pass), concluded that Mexican cartels earn no more than $2 billion moving marijuana across the Southwest border and that the groups derive 15 to 26 percent of their revenue from marijuana sales.

The Rand study authors estimated that legal marijuana use in California, a state that consumes about one-seventh of all the pot smoked in the United States, would cost the cartels 2 to 4 percent of their revenue. So losing consumers in states such as Washington and Colorado that have a smaller population might not affect the cartel bottom line by much.

U.S. government estimates of drug cartel profits, however, are much higher.

"Marijuana is an important part of their business, but not the most important. Most people agree it's about 20 percent of their revenues, and so two small U.S. states legalizing marijuana won't really impact their market share very much," said Eric Olson, deputy director of the Mexico Institute at the Wilson Center in Washington.

But Olson said the incoming Mexican president will be watching closely.

"There is a sense of frustration throughout Latin America about the steep costs of confronting drug trafficking. And these votes in the United States, and the reaction to them, might signal a willingness for the countries to think outside of the box on drug policy."

Whether the loss of some marijuana revenue will reduce killings in Mexico is even more uncertain, as much of worst violence is attributed to crime rings that have branched out from drug smuggling to human trafficking, extortion, kidnapping, oil theft and DVD piracy.